Percutaneous angioplasty is a therapeutic medical procedure that can increase blood flow through a blood vessel. It can sometimes be used as an alternative to coronary by-pass surgery for example. An elongated catheter having a deflated balloon at its distal end is guided through a patient's cardiovascular system to the coronary artery of the heart. The balloon is inflated to compress deposits that have accumulated along the inner walls of the coronary artery to widen the artery lumen and increase blood flow.
A known technique for positioning the balloon catheter uses an elongated guidewire that is inserted into the patient and routed through the cardiovascular system as guidewire progress is viewed on an x-ray imaging screen.
Representative prior art patents that disclose flexible, elongated guidewires are U.S. Pat. No. 4,545,390 to Leary, U.S. Pat. No. 4,538,622 to Samson et al. and U.S. Pat. No. 3,906,938 to Fleischhacker and U.S. Pat. No. 4,846,186 to Box et al. The Box et al. patent is incorporated herein by reference.
One problem with currently available guidewires concerns the visibility of the guidewire. If the guidewire is fully opaque on a viewing screen, it can hinder viewing of post angioplasty angiograms used in studying the results produced by the angioplasty, especially in the arterial area proximal to the coil/tip section. Guidewires that have only an opaque tip do not adequately depict the arterial path on the viewing monitor.
U.S. Pat. No. 4,922,924 to Gambale et al. concerns a guidewire for use in placing a catheter. The guidewire includes a coil assembly that is formed from a highly radiopaque coil and a non-radiopaque coil, arranged in bifilar arrangement to define a moderate radiopacity guidewire section.